Debunking Common Brain Myths

Sam Wang is an associate professor, Department of Molecular Biology and the Princeton Neuroscience Institute.

Wang grew up in California and studied physics at the California Institute of Technology. Seeking his Ph.D. at Stanford University, he switched to neuroscience. He has worked at Duke University as a postdoctoral fellow and aided political leaders as a Congressional Science Fellow. After completing his postdoctoral studies, he spent two years at Bell Laboratories in Murray Hill, N.J., where he learned to use pulsed lasers to study brain signaling before coming to Princeton.

Wang, who has published more than 40 articles on the brain in leading scientific journals. His educational reach extends past the laboratory and classroom in his books, popular articles and efforts to convey neuroscience to interested nonscientists.

21 May, 2009

Topic: Sam Wang on the 10% myth

Sam Wang: The 10% myth is a funny one because it doesn’t come from an identifiable neuroscientific discovery. The earliest mention of the idea that you only use 10% of your brain comes from the motivational speaker and writer Dale Carnegie in “How to Win Friends and Influence People.” Actually, Lowell Thomas said in the preface. And before that, the only statement that resembles that is again, as I mention before, this pioneer of psychology and as it turns out neuroscience, William James. He told audiences that we only meet a fraction of our full potential.

And I think that statement is true because it certainly the case, for instance, that IQ scores have gone up a few points per decade in modern times, which suggest that there’s some influence in the environment on what we can become.

In that sense, we maybe still exploring our full potential. But the 10% idea is literally not true. If you damage any part of the brain, you can… If any part of the brain is damage, it can lead to deficit as a function. For instance, if I damage… If a person experiences damage to the cerebellum, which guides smooth movements, then people are unable to move smoothly, unable to learn new things like a dance step or a tennis stroke. And you can come up with similar kinds of observations for all parts of the brain so you really need the whole thing.

You need a 100% of your brain. If any part of your brain went missing in action, you would notice and you’d be sorry. Well, depending… Actually, depending on the part of the brain, you might not be sorry.

Topic: Sam Wang on alcohol and the brain

Sam Wang: A really common belief about the brain that you hear at parties is the idea that drinking alcohol kills brain cells. People make light to this all the time. The truth is that alcohol can damage the brain but it’s highly unlikely to kill brain cells. When people look at the brains of alcoholics’ postmortem, it takes decades of drinking before loss of brain cells becomes apparent, okay? So… And in fact, loss of brain cells, when it does eventually happen, it’s associated with a profound loss of memory, a thing called Korsakoff’s syndrome. And that happens after decades of drinking. Now, having been said, alcohol does cause damage to the brain.

So one thing that has been observed is that heavy drinking for years does lead to shrinkage of the brain. And that is probably the source of the idea that alcohol kills brain cells that you can observe shrinkage of the brain.

Now, let’s put these two together. Alcohol causes shrinkage of the brain but the cells don’t diminish the number so what that suggest is there something about each individual cell that shrinking. And what’s believed is that the trees, the dendritic trees that neurons have, may retract a little bit and they’re constantly growing and shrinking. And so, what’s believed is that, perhaps, they retracted a little bit. And the practical implication of this is that if you stop drinking, then they, perhaps, will grow back. Okay. So that’s the practical implication.

And so, even though the idea is a myth, it’s still important to remember that drinking alcohol is not a good thing for your brain when you do it for many years at a time. I have more that I forgot to give so can I fill that in? Sorry about that. Okay. The other side of the coin is that moderate amounts of alcohol are not harmful and, in some cases, can even be helpful. And there’s a very specific case, which is red wine. It turns out that moderate amounts of red wine seem to have some kind of protective effect on brain function especially as you are getting older.

And it’s not known exactly why but there’s a general principle, which is that things that are good for your heart and your cardiovascular system are also good for your brain. And so, there are health benefits that have been demonstrated of red wine, some of which are mediated through the compound resveratrol. And what’s been observed is that up to 3 glasses of red wine per day for men and up to 2 glasses for women is either neutral or slightly beneficial for brain function. And that adds up to a bottle for a couple per day so that’s easy to remember.

Topic: Sam Wang on drugs and the brain

Sam Wang: All drugs exert their effects by acting on some kind of receptor on the brain. In many cases, that receptor is identified.

To pick an example, cocaine and methamphetamine act upon a molecule whose job it is to suck up dopamine back in to cells after it’s been released. And so, those are blockers of dopamine re-uptake. Another example is LSD, which acts upon very specific receptors for the neurotransmitter serotonin. So all of these acts upon different receptors to cause their effects to cause hallucinations or intoxication or feelings of confidence or what have you. And a consequence of that is that they’re addictive to different degrees. So, for instance, alcohol is addictive. Nicotine in cigarettes is addictive. Cocaine and methamphetamine are highly addictive. And so, those tend to lead to dependencies and bad effects that you feel for many years and you get trapped in using those things.

Other drugs seem to not have much addictive potential, and you mention LSD. LSD is not addictive so far as anyone can tell and does not seem to lead to long-term harmful effects. No, it does not. All these drugs act on different things. I mean, they’re not clean laboratory design experiments that we can perform in our brains. They tend to have lots and lots of different effects. I think that if alcohol were to appear as a new drug today, I think it would be basically banned immediately because of all the drugs that are available, it’s this nasty solvent that can kill cells, that can cause dendrites to shrink, that can lead to us to be unable to operate machinery safely, and can cause people to beat up their love ones and spouses, I mean, it’s a fairly serious drug. But it’s been around long as since though through familiarity, we think its okay. Wine, beer, liquor, whatever, it’s fine. And the flipside of that is something like, say, LSD, something that’s relatively recently come into use. And there’s no denying if you were to take LSD, you would need to be in a safe place and be important to put yourself in a position where you didn’t hurt anybody or hurt yourself.

There are not long-term damaging effects of LSD the way that they are for alcohol. And so, there’s this curious property of these drugs that sometimes are… perceptions of them as a society are not quite the same as the mechanisms of what they do to the brain. One drug that’s pretty unambiguously bad is cocaine methamphetamine. A rule of thumb seems to be that drugs that blocked dopamine uptake have a lot of potential for addiction. And that’s because addiction seems to work through dopamine pathways on the brain. And they lead to dependencies that can be very bad for you. So dopamine uptake blockers seem to be bad for the brain.

Topic: Sam Wang on book smarts vs. street smarts

Wang: I think Goleman’s ideas are very interesting. This old school idea that basically no one believes anymore, which is that intelligence is just described by one factor, a perimeter that people use to call G for general intelligence. And either you had more of it or you had lots of it. And a certain element of that is still true because there is a thing that you can measure on tests that has to do with fluid problem-solving that one… that people still call G. And so, that part’s true.

But I think one thing is interesting there, with Goleman, is the idea that there are many mental capacities that we have and they are, to a certain degree, independent with one another. Now, it turns out they are less independent than one might imagine. It turns out that on average, people who are better at, say, IQ tests on average tend to be better in social intelligence. Now, that might be hard to believe when you go to university and quiz your average mathematician. Not all those people are all that socially advanced. But nonetheless, there is a positive relationship among these things and they rely on slightly different brain systems. So I think it’s possible for these capacities to be somewhat independent of one another.

Question: What is a creative brain?

Sam Wang: Creativity is a pretty general concept. And in order to reduce it into something you can study, you have to start thinking about a problem that you can give somebody in the laboratory.

And so, for instance, there’s a kind of problem-solving called divergent thinking, finding solutions that other people do not find at the same problem. Okay. So, for instance, an example of creativity, an animal might be; if you have a crow; imagine a box in which the box can either be opened by flipping the lid like this or by pulling on the lid like this. And what ethologists have discovered is that when you take a crow, most crows will learn how to open the box like this and flip it like that. Okay.

And occasionally, a crow will have the innovative thought of pulling the box the other way. Okay. So that’s an example of divergent thinking that you can identify in a crow. And crows even have social learning.

So, for instance, if one raven sees another raven do this, then, in fact, it can learn to do the innovative way of solving the problem right away. And that’s an example of social learning. And this is clearly something that’s very highly developed in us, right? Our cultural evolution occurs far, far faster than biological evolution. And so, that kind of creativity of tool making is something that crows have a surprising amount of… that we have. And so, one question is how to study these things. And you have to cook up tasks that are more germane So, for instance, one example is left-handers.

On average, left-handers seem to be more prone to divergent thinking and creative ways of solving problems at least in the laboratory context. So that’s one example of a demographic that seems to have more of this, whatever it is.

Topic: Sam Wang on left brain vs. right brain

Sam Wang: So the popular belief about the left brain and the right brain… And people are usually talking about the cerebral cortex when they talk about these things is that the left half of the brain is rational and problem solving and uncreative. And somehow, the right brain is creative. It can help you draw better, right? Now, the truth is more complicated. Because, in fact, the hemispheres of the brain… Because the hemispheres of the brain are heavily interconnected by the structure, that’s… basically, this dense band of fibers called the corpus callosum.

And what seems to be really the case is the left half of the brain is important for mathematical reasoning, for generating language, but it’s also a storyteller. So, for instance, in split brain patients who have their corpus callosum cut, when you show a picture and you play a picture association with the right half of the brain by showing the left half of the world… of the person’s world things and ask the right half of the brain to do something, the right half of the brain will happily play picture association. Then, if you ask the person, why did you make that association, the left half of the brain makes up a story.

So, for instance, you could show the right half of the brain a snow scene and a chicken claw and the left brain sees the chicken claw, the right brain sees the snow scene and then you ask the right brain what goes with it, and the right brain will pick a shovel. And then, you ask the left brain, why did you pick a shovel, and the left brain saw the chicken claw and the left brain makes up this crazy story. The left brain will say, well the chicken lives; that’s a claw, it goes with the chicken, the chicken lives in a coop, you need a shovel to shovel out the chicken coop. And it’s this totally made-up story. And so, it turns out that the left half of the brain is perfectly capable of making up stories. And so, that seems to be; that sort of creative, right? That doesn’t fit the stereotype.

I think what’s more the case is that the right brain is important for certain things. So, for instance, the left brain produces language, the right brain produces porosity, which is the emotional content of a language. In many ways, the right brain, on the other hand, is quite concrete. And so, I think the story is more complicated. And I think these cultural ideas about left brain, right brain have basically blown up all out of proportion to what scientists have actually found about the left and right brain.